This invention is generally directed to improvements in antenna isolators. It is particularly directed to a method of fabricating a bleeder resistor for use in such an isolator.
It is now widely recognized that isolation should be provided between a television receiver's tuner and the cable which carries the television signal to the tuner. With such isolation, any power line voltage which may appear on the tuner is inhibited from reaching the cable input to the tuner. Potential shock hazards to one who touches the cable input are thus eliminated.
A preferred type of isolator is disclosed in U.S. application Ser. No. 282,824, filed July 13, 1981, now U.S. Pat. No. 4,399,419, and assigned to the assignee of the present invention. Briefly, the above-referenced application discloses a small isolator which includes a pair of dielectric elements which sandwich a ferrite element. The three elements may be built into a cable, or into a connector for the cable, such that the dielectric elements provide a capacitive coupling for the desired television signal and simultaneously inhibit the conduction of AC power line currents. The ferrite element absorbs ambient electromagnetic interference to protect the transmitted field within the cable. A small but reliable housing for the three element isolator described above is a connector assembly or plug.
To remove accumulated charge from the capacitors formed by the dielectric elements, a bleeder resistor may be included as part of the isolator. However, problems arise in attempting to include a suitable bleeder resistor in the isolator's housing.
First, the resistor must necessarily occupy very little space if it is to be contained within a plug. Secondly, the value of the resistor should not change substantially as a function of voltage across it. These two criteria make it difficult to use a conventional discrete resistor as a bleeder. In addition, any such bleeder resistor must withstand relatively high operating voltages and test voltages to meet existing safety standards. Equally desirable is the ability to manufacture the bleeder resistor easily in high volume production.
Accordingly, it is a general object of the invention to provide an improved method of fabricating a bleeder resistor for use in an antenna isolator.
It is a more specific object of the invention to provide a method of economically fabricating a very small bleeder resistor whose value does not change substantially as a function of applied voltage, and which can withstand relatively high test voltages and operating voltages.